1. Field of the Invention
The present invention relates to, a ladder filter, and more particularly, to a ladder filter for use in a communication device, such as a portable telephone or the like.
2. Description of Related Art
A conventional type of ladder filter has a structure wherein piezoresonators and terminals are stacked and contained in a box-type case. At least one of the terminals has a first electrode portion and a second electrode portion which are mutually folded, and the first electrode portion and the second electrode portion each have a projection for supporting a piezoresonator.
A possible way of downsizing the ladder filter is to use a thin plate as the material of the terminals. However, the terminals must have a strength over a certain degree, and the plate must have a thickness which guarantees the strength.
Another way of downsizing the ladder filter is to provide low projections on the first and the second electrode portions. In this case, however, if a piezoresonator is placed in the case in a slanted position, the peripheral portion of the piezoresonator may come into contact with the first and/or the second electrode portions of the terminal. Then, the piezoresonator may be influenced by damping, and the electrical characteristics of the ladder filter may be lowered.